体会String对象的match方法和new RegExp(re).exec(str)的区别

var str ="cat matt daa bat"
var re = /at+/g;
var match = str.match(re);
console.log(match);
console.log(new RegExp(re).exec(str));

输出如下

[ 'at','att','at' ]
[ 'at',index: 1,input: 'cat matt daa bat' ]
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